Responsible for communications between enddevice and nics
allows upper layer protocols to access the physical layer zb encapsulates L3 Packets into L2 Frames
Performs error detection and rejects corrupt frames
- Unicast
- 1 zu 1
- SRC: A1:B1:C1:D1:E1:F1
- DST: A2:B2:C2:D2:E2:F2
- Brodcast
- 1 zu mehrere (1 zu N)
- SRC: A1:B1:C1:D1:E1:F1
- DST: FF:FF:FF:FF:FF:FF (nur 1er in Binär)
- 2 sublayer
- Logical Link Control(LLC)
- communicates between upper layers and the device hardware at the lower layers
- Media Access Control(MAC)
- responsible for data encapsulation and media access control
- Logical Link Control(LLC)
- four basic L2 functions at each hop
- Aceepts a frame from the network medium
- De-encapsulates the frame to expose the encapsulated packet.
- Re-encapsulates the packet into a new frame
- Forwards the new frame on the medium of the next network segment
- Standards
- Institute for Electrical and Electronic Engineers (IEEE).
- International Telecommunications Union (ITU).
- International Organizations for Standardization (ISO).
- American National Standards Institute (ANSI).
- Topologies
- Physical topology
- Logical topology
- Wan topologies
- Point to point
- permanent link between two endpoints → simplest and most common
- Hub and spoke
- similar to star topology central site iNtErCoNnEctS sites through point to point links
- Mesh
- high availability → every end system is connected each other
- Point to point
- Half duplex communication
- one device send/receive at a time on a shared medium
- used on wlans (and legacy topologys zb bus)
- Full duplex communication
- both devices simultaneously transmit/receive on a shared medium
- ethernet switches operate in full duplex